Generally, a seatbelt alarm device is mounted in a vehicle for determining whether or not a seatbelt is worn and generating a seatbelt-wear alarm when it is determined that the seatbelt is not worn.
In one known seatbelt alarm device described in JP-1999-70855A, a seat sensor is provided to detect whether or not a passenger sits on a seat and then generates a corresponding signal. Furthermore, a seatbelt sensor is provided to detect whether or not a seatbelt of the seat is worn and then generates a corresponding signal. When it is determined that a passenger sits on the seat without wearing the seatbelt according to the sitting signal and the seatbelt signal, the seatbelt alarm device generates a seatbelt-wear alarm for inducing the passenger to wear the seatbelt. This seatbelt alarm device can be suitably used for seats in a vehicle.
For a seat on which a child seat is mounted with the seatbelt, the seat sensor will detect the weight of the child seat and generate a corresponding sitting signal. Furthermore, the seatbelt sensor will detect that the seatbelt is worn and generate a corresponding seatbelt signal. Thus, the above-described seatbelt alarm device determines if the seatbelt of the seat is worn irrespective of whether a child sits in the child seat or not.
However, in the case where the child seat is mounted on the seat with fasteners or the like as opposed to the seatbelt, the seat sensor will detect the weight of the child seat and generate the sitting signal and the seatbelt sensor will detect that the seatbelt is not being worn. Accordingly, the seatbelt alarm device falsely determines that a passenger sits on the seat without wearing the seatbelt, thereby generating an incorrect seatbelt-wear alarm.
Therefore, the vehicle may be provided with a switch near a driver so that the driver can manually cancel the seatbelt-wear alarm when the child seat is mounted to the seat. However, this method may require frequent operation of the switch by the driver, which may become impractical or inconvenient.